An inkjet printing system typically includes one or more printheads and their corresponding ink supplies. Each printhead includes an ink inlet that is connected to its ink supply and an array of drop ejectors, each ejector consisting of an ink chamber, an ejecting actuator and an orifice through which droplets of ink are ejected. The ejecting actuator may be one of various types, including a heater that vaporizes some of the ink in the chamber in order to propel a droplet out of the orifice, or a piezoelectric device which changes the wall geometry of the chamber in order to generate a pressure wave that ejects a droplet. The droplets are typically directed toward paper or other print medium (sometimes generically referred to as paper herein) in order to produce an image according to image data that is converted into electronic firing pulses for the drop ejectors as the print medium is moved relative to the printhead.
Motion of the print medium relative to the printhead may consist of keeping the printhead stationary and advancing the print medium past the printhead while the drops are ejected. This architecture is appropriate if the nozzle array on the printhead can address the entire region of interest across the width of the print medium. Such printheads are sometimes called pagewidth printheads. A second type of printer architecture is the carriage printer, where the printhead nozzle array is somewhat smaller than the extent of the region of interest for printing on the print medium and the printhead is mounted on a carriage. In a carriage printer, the print medium is advanced a given distance along a print medium advance direction and then stopped. While the print medium is stopped, the printhead carriage is moved in a direction that is substantially perpendicular to the print medium advance direction as the drops are ejected from the nozzles. After the carriage has printed a swath of the image while traversing the print medium, the print medium is advanced, the carriage direction of motion is reversed, and the image is formed swath by swath. In order to accomplish the motions necessary for printing in a carriage printer, there are typically at least two motors—the motor for print medium advance, and the motor for carriage motion. The examples described in the present invention relate to a carriage printer architecture.
As carriage printer technology matures, there is a need to offer more functions and at lower cost. While previous printers may have dedicated a separate motor (in addition to the motor for paper advance and the motor for carriage motion) to drive an additional function, offering the function without the need for an additional motor is desirable.
It is known in the prior art to use the power of the paper advance motor to operate the various functions of the maintenance station in an inkjet printer. U.S. Pat. Nos. 6,846,060 and 7,225,697, for example, describe power transmission mechanisms that are selectively engaged or disengaged depending on whether or not the carriage is parked at the maintenance station. If the carriage is parked at the maintenance station, a feature on the carriage enables the power transmission mechanism to be engaged. By this means, the maintenance station functions including wiping and capping may be powered by the paper advance motor. When the carriage moves away from the maintenance station, the feature on the carriage no longer enables the power transmission to be engaged for maintenance operations, so that the paper advance motor is used for moving paper through the printer.
For some modes of printing, it is necessary to operate different paper advancing rollers at different times or in different directions. In such a case, a mechanism such as those in '060 and '697 which only allows engagement when the carriage and printhead are parked at the maintenance station is not sufficient.
There is a need, therefore, for a selector mechanism that can operate in different selection positions even after the carriage has moved away, and that can selectively engage one or more of a plurality of functions, driven selectively by a single motor.